Protective means for electric furnaces



Abert n. @ta

Jigw His Attorneg.

inventor www A. N. @TES PROTECTIVE MEANS FOR ELECTRIC FURNAGES Filedsept. 10, 1925 Patented Apr. 9, 1929. p

UNITED STATES ALBERT N. OTIS, OF SCENECTADY, NEW

1,708,112 PATENT ori-ica PROTECTIVE MEANS FOR ELECTRICPFURNACES.

Application led September 10, 1925. `Serial No. 55,584.

My invention relates to protective means for electric furnaces, and hasfor its object ,the provision of improved means for opening the heatingcircuit of the furnace upon the occurrence of a predetermined maximumtemperature therein. I

More specifically, my invention relates to protective means for vhightemperature electric furnaces such as are used, for example, in the heattreatment of metals for annealing and hardening purposes, etc.Suchfurnaces are ordinarily provided withl a resistance heater andoperate at temperatures around` 90()O C., which is near'the maximum safeworking temperature of the resistor so that care must be taken toprevent damage to the resistor by overheating. One form of protectivemeans for furnaces of this type, in the nature of a fuse, is describedand claimed inv Patent No. 1,490,408 to Van- Aller, dated.' April 15,1924, of which my invention is an improvement. In such devices theprotective means may be inserted through a suitable aperture in thefurnace wall so as to be eX- posed to the heat of the furnace.

In carrying out my invention, I provide an elongated support made ofinsulating mat-erial and provided with longitudinal apertures throughwhich a fuse wire is threaded in such manner that the ends of the fusewire are at the outer ends of the tsupport and the central portion ofthe fuse wire at. the inner end of the support is exposed to the heat ofthe furnace. For a more complete understanding of my invention referenceshould be had to the accompanying drawing in which Fig. 1 is a plan Viewof protective means embodying my invention; Fig. 2 is an enlargedfragmentary sectional view of the device shown in Fig. 1 taken along theline 2-2 'of Fig. 4 looking in the direction of the arrows; Fig. 3 is afragmentary sectional view taken along the line 3 3 of Fig. 4 looking inthe direction of the arrows; Fig. 4 is an end view with the coverremoved; Fig. 5 is a detail view; while Fig. 6 is a diagrammatic viewshowing the application of my invention to an' electric furnace.

Referring to the drawing, I have shown my invention in one form ascomprising a plurality of members or blocks which may be cylindrical inform, and which are made of suitable insulating material such asporcelain. These insulating members are similar in construction and areeach provided with four longitudinal apertures 11, 12, 13 and 14 (Fig.5) spaced at equal intervals thelr perlpheries.. The apertures 11 iidmlgare somewhat larger than the apertures 12 and 14, and are adapted toreceive a U shaped clamping member or rod 15 which is threaded throughthese apertures in a series of the insulating members 10 so as to holdthem in end to end abutting relation, as indicated in Fig. 2.Preferably, a specially formed insulating member 16 1s provided at theend, which member is sllpped on the clamping rod `15 first, thisinsulatlng member being provided with a transverse groove 17 whichconnects its apertures 11 and 13 and in which the transverse centralportion 18 of the supporting rod lies. After `the insulator 16 has beenslipped on the clamplng rod, the desired number of insulators 10 areslipped on together with a special- ]y'formed insulating member 19 atthe opposite o r outer end. This member 19 is likewise provlded withapertures 11, 12, 13 and 14, and after it is put in place washers areplaced over the threaded ends of the cla1nping rod 15 and nuts 20 and 21applied and turned down tightly so as to securely clamp the variousinsulating members together and thereby form a rigid elongatedinsulating support.

The outer insulating member 19 is cylind rical in shape, but, as shownin Fig. 2, is conslderably larger in diameter than the insulators 10whereby a metallic casing or head member 22 may be secured by clampingit to a metallic ring 23 which is slipped over the insulators 10 andseated against the ledge formed by the projecting edge of the insulator19. Metallic connector members 24 and 25 (Fig. 3) are seated inlongitudinal apertures in the insulator 19, these members being providedwith central longitudinal apertures 26 and 27 which correspond with theaper- 'YORK, ASSIGNOR TO GENERAL ELECTRIC COMPANY, A. CQRPORATION 0w NEWYORK.

tures 12 and 14 of the insulators 10. Suitable 95 clamping screws 28-31inclusive are provided in the connectors 24 and 25, transverse openingsbeing provided in the insulator 19 so that access may be had to theseclamping screws by removing the cover 22.

It will be observed that the alignedapertures 12 form a continuous ductleading longitudinally throughout the entire length of the fuse supportand likewise the aligned ap. ertures 14 form a similar longitudinalaperture. A. fuse wire 32 is threaded through these longitudinalapertures, it being substantially U shaped with its central portionextending across the inner end of the support,

e., across the end of ineinhers lo, and its ends lying in the connectorsand 25 in which thev are secured by means or the screws l inelectrically ccrducting el 'ne central ne-'ca having point.

placed'on the 'inse "iure vaeey pos vely opens the elect le the fuseWire. 2Conductors 341. "a the ends orn the i'use s are inserted, .eupoeisuiator is provi 'ovide space for the vresistor is disconnectedfrom its supply source v42 upon the occurrence oi` a predeterminedmaximum temperature hy reason of the melting of the inner portion of thefuse Wire which opens the circuit ot the operating coil 39..

While l have described my invention as embodied in concrete :form and asoperating in a specific manner in accordance with the provisions or" thepatent statutes, it should he understood that l do not limit myinvention thereto, since various modifications thereof will suggestthemselves to those skilled in the art Without departing 'lrom thespirit oi my invention, the scope or which is set forth in the annexedclaims.

What I claim as nevel and desire to secure by Letters Patent of theUnited States is:

1. ,A protective device for electric furnaces comprising an elongatedheat `refractory electrically insulating support provided Withlongitudinal apertures, said support being adapted to bel inserted in anaperture in the furnace Wall, and a Wire threaded through said apertureshaving its ends at the outer end thereof and having a fusible portionextending across the inner end of said'support so as to be exposed tothe heat oi said furnace.

2. A protective device 'for electric furnaces comprising a plurality ofheat refractory insulatiugn members provided ,means :tor se f l relationvn 'is to form i "n 'supper' in a iur ner end the heat the furnace.

plurality of insulating members ided with apertures, clamping means ex--ding through some oi: said apertures to se- "e said members together inabutting rela- Qo/ 'orm an elongated se support adapted to oe in- :naceand a ireaded 'through the remaining' ap- .said inernhers havingl aportion exse 1, e

Jures in i: said s eport.

4:, orotec ive device for electric furnaces conaprisingg,` a pluralityof insulating ineinbers provided with apertures, a ll shaped clampingrod threaded through two of the apertures or said members so as tosecure said members together in abutting relation and thereby form anelongated insulating support adapted 'to he inserted in an aperture in afurnace Wall, and a use Wire threaded 'through the remaining aperture insaid menihers having a portion extending across the inner end oi' saidsupport so as to be exposed to the heat of said furnace.

3. A protective device ior electric furnaces comprising a plurality or'insulating ineinoers, each of said members oeing provided with i'ourspaced apertures, a U shaped clamping. rod threaded through tvvo of saidapertures so as to secure said memhersin abutting relation and therebyform an elongated insulating support adapted to he in-v sei-ted in anaperture in a furnace wall, a fuse Wire threaded through the remaining,-two of.

se ce ci or said support. A

Witness whereof, It have hereunto set my hand this 9th day of September,1925.

ALBERT N. OTIS.

l protective device ior el ctric Afurnaces sup- :o the heat of saidliurnace the innere lic protecting head secured to the outer end dll

